Crystal Cavern (ちかたいが Magicant Underground in Mother), is a location found in EarthBound Beginnings. It is a short dungeon located in Magicant, found via a hole in the eastern portion of Magicant, not far from the castle. Entering the cavern, there are two holes; the proper order to visit them in is right, left, left, and right. There is a pit leading into a room with the Onyx Hook, an item necessary to teleport back to Magicant's center; but The Fish enemy must be defeated first. A sleeping dragon rests here, but cannot be awakened until Ninten is level 25. In order to exit the Magicant Underground the player must speak to the Forgotten Man.
In the original Famicom release of the game, the layout of Crystal Cavern was more complex with longer hallways. This was simplified in later releases. In the Encyclopedia MOTHER companion guide, the Cavern's name is given literally as 'underground stream'.